Machanics
posted by Anonymous .
An electron moving at a speed of 5 multiply by 10 raise to power six m/s was shot through a sheet of paper which is 2.1 multiply by 4cm thick.the electron emerges from the paper with a speed of 2 multiply by 10 raise to power six m/s,find the time taken by the electron to pass through the sheet.

vf  vi = 5*10^6  2*10^6 = 3*10^6
where vf is the final speed and vi is the initial speed.
Assuming a constant deceleration, the electron passes through 2.1 multiply 4cm = 8.4 cm of paper.
8.4 = 1/2*a*t^2
deltav = 3*10^6 = a*t
where a is the acceleration, t is the time. You have two equations with two unkowns (a and t). Use algebra to solve for t, the time taken by the electron to pass through the sheet.